Observations

Description

Valves are lanceolate to elliptic-lanceolate with narrowly rounded apices. The axial area is very narrow and linear. The central area is highly variable in shape and size, from elliptic to transversely rectangular, and often asymmetric. The raphe is filiform with tear-shaped proximal raphe ends that are deflected slightly to one side. The lineate striae are radiate, becoming convergent at the apices. Striae are unevenly spaced around the central area. The areolae are easily observed under LM and number 28-34 in 10 µm.

Valves are lanceolate to elliptic-lanceolate with narrowly rounded apices. The central area is variable in size and shape, and is typically asymmetric. Striae are irregularly spaced around the central area. The proximal raphe ends are bent slightly to one side.

Compare

Navicula libonensis has more lanceolate, less elliptic valves with narrower wedge-shaped apices and straight proximal raphe ends. Valves of Navicula erifuga have a smaller central area bordered by evenly spaced striae.

Links & ID's

Index Nominum Algarum (INA)

California Academy of Sciences (CAS)

North American Diatom Ecological Database (NADED)

NADED ID: 46496

Autecology Discussion

Navicula eidrigiana is an uncommon resident of brackish springs and small streams on the Northwestern Great Plains. It typically prefers waters with a higher electrolyte content than Navicula libonensis. Some of the specimens on this page come from Iron Spring on the Custer National Forest in Carter County, Montana (photo below). Iron Spring has a pH of 8.32, conductivity of 2740 µS/cm, and temperature of 22.2 C.

Images

Iron Spring, Custer National Forest, Carter County, Montana: home of Navicula eidrigiana.